The history of public health is a chronicle of billions of lives saved from preventable deaths and diseases, thanks to the heroic work of generations of people. And yet, most people have never heard of them, or ever notice the public health protections that keep them safe every day.

On March 26th on PBS, watch The Invisible Shield, a four-part documentary supported by Bloomberg Philanthropies that tells the story of how we’ve built a world where people are living longer, healthier lives than ever before — and celebrates the unsung heroes who made it possible.